Bituminous flame resistant compositions and articles coated therewith



2 14 4?; was

Kiri

Patented June 1,

overtly no BITUMINOUS FLAME RESISTANT COM- POSITIONS AND ARTICLES COATEDTHEREWITH John W. Olson, Hastings on Hudson, N. Y., and Charles W.Bechle, Sycamore, 111., asslgnors to Anaconda Wire and Cable Company, acorporation of Delaware No Drawing. Application October 15,

Serial No. 415,144

7 Claims. (Cl. 106-15) This invention relates to flame-resistantcompositions, and is concerned particularly with the provision of a newsynthetic organic flame-resistant composition having flame-resistantproperties generally more uniform than and superior to the correspondingproperties of heretofore known organic flame-resistant materials. Theinvention further contemplates articles of manufacture comprising a basestructure having thereon a coating of the new flame-resistantcomposition.

Organic flame-resistant materials have long been used to reduce theinflammability of articles composed either wholly or in part ofcombustible organic substances. For example, electric wires insulatedwith rubber and surrounded by an organic fibrous jacket impregnated withasphaltic moisture-proofing compounds have been coated withflame-resistant composition to lessen the inflammability of theinsulation and so to reduce the fire-hazard of the wiring installation.Similarly, it has been proposed to lessen the inflammability of roofingmaterials composed of a backing sheet and coated or impregnated with amoisture and weather-resistant material, such as asphalt or tar, bycoating such roofing with a flame-resistant composition.

The flame- 'st ant material most commonly used heretofore hasbeenjstearig pitch. This material is the residueremaifliiig iifthestills after completion of the distillation of fatty materials, such astallow. It is pitchy in character, usually black in color, and rathersticky even at ordinary temperatures, although its softening point isusually quite high. Upon heating to a temperature sufficiently above itssoftening point, it becomes fluid, and in this condition it may beapplied in the form of a relatively thin coating to wire, roofingsheets, and other articles,

Stearin pitch as a flame-resistant material for use on wires, roofingmaterials, and the like possesses a number of drawbacks. In the firstplace, its flame-resistant properties are'extremely variable, dependingupon the particular type and grade of material from which it is producedand further depending upon the manner in which it is produced. At oneextreme, some commercial stearin pitches are quite readily inflammableand are therefore valueless Where flame resistance is a desired quality.At the other extreme, some commercial stearin pitches possess very goodflame-resistant characteristics. Other grades of stearin pitch fallbetween these extremes in their flame-resistant properties. It istherefore difficult consistently to procure stearin pitch of uniformlygood flame-resistance. In the second place, stearin pitch forflame-resistant uses is a relatively expensive commodity, and its priceis subject to considerable fluctuation from time to time. In the thirdplace, the natural stickiness of stearin pitch renders it unsatisfactoryas a finishing coat on articles, such as wire or sheet roofing, whichare coiled, rolled or stacked for shipping. Although generally sucharticles are best made flame-resistant by applying the stearin pitch asthe final coating, this is not usually practicable because when the wireor roofing is coiled or rolled the stearln pitch causes the adjacentturns or layers to stick together.

The present invention provides a new and improved flame-resistantcomposition which can be manufactured from readily available materialsat a cost considerably less than the average price of stearin pitch;which can be manufactured with uniformly high flame-resistantproperties; which may be made much less sticky than stearin pitch; andwhich with these advantages can be made even more flame-resistant thanthe best grades or stearin pitch heretofore available.

The new flame-resistant composition is of such character that it may beapplied to the surface of an article and forms thereon a hard permanentcoating. It is stable at temperatures incident to its normal use, but itis characterized by pufilng and coking with the formation of anintumesced, diflicultly combustible coky mass when exposed to flame. Thecgrnposition come.

prises bitumen which imparts to the composition the iiroperty'ofionninga coky mass upon burning, to which bitumen has been added a substancewhlch is characterized by puifing and becoming highly intumescent whenexposed to flame, the added substance being a substantially neutralsulphated or phosphated acid petroleum sludge derivative. Compoundscontaining sulphated or phosphated derivatives of higher fatty acids,higher fatty acid esters, and higher fatty acid alcohols, characterizedby pufiing and becoming highly intumescent when exposed to flame, aredescribed and claimed in our copending application Serial No. 415,145,filed October 15, 1941,

Bitumen is not highly flame-resistant and is incapable of impartingflame-resistance to articles to which it is applied. This probably isdue to the fact that when bitumen is ignited on the surface of aninflammable article, any coky masses that may be formed are in suchclose contact with the inflammable article itself that combustionproceeds quite readily. However, when an acid petroleum sludgederivative is added to the bitumen, and the resulting mixture is exposedto a flame, it puffs and forms a highly intumesced, difiicultlycombustible= coky mass which is spaced from any underlying inflammablematerial. The coky mass thus is maintained out of close contact withreadily inflammable material which would enable it to burn relativelyeasily, and at the sam time the intumesced coky mass serves to insulateunderlying inflammable material from the flame. Bitumens, andparticularly asphaltic bitumens of at least moderately high softeningpoints (upwards of 175 F.) have the property of burning with theformation of a coky mass and are especially satisfactory for thecomposition.

The acid petroleum sludge derivatives employed in the new compositionare compounds containing sulphur-oxygen and phosphorus-oxygen radicals,such as sulphate, sulphone, and phosphate radicals, which arecharacterized by pufiing and becoming highly intumescent when exposed toflame. These compounds by themselves are not especially flame-resistant,but in combination with bitumen form compositions having excellentflame-resisting properties.

Sulphated or phosphated petroleum hydrocarbons (either pure or in theform of mixtures) may be used successfully in preparing the newcomposition. Such sulphated or phosphated products may be produced bytreatment of petroleum hydrocarbons with sulphuric or phosphoric acid.Especially economical commercial sources of mixtures of sulphatedproducts of this character are the acid petroleum sludge resulting fromsulphuric acid refining of petroleum, and the acid oil remaining afterremoval of tar from such acid sludges. These products are of complicatedand uncertain composition, but they usually contain monoand dialkylsulphuric esters, sulphonates of aliphatic and. aromatic compounds,and-other compounds. These products may be used directly in preparingthe new composition.

The sulphated and phosphated compounds prepared by treatment ofpetroleum oils with sulphuric or phosphoric acid are commonly acidic inreaction (unless purified). Compounds having an acid reaction areeffective for producing flame-resistant compositions, but thepresence ofacid components is undesirable for many of the uses to which the newflame-resistant composition is adapted. Hence it is generally mostsatisfactory to employ neutralized (or naturally neutral) sulphated orphosphated compounds. In many cases such neutralized derivatives may beprepared by washing the acidic sulphated or phosphated compound toremove excess acid, and then, if necessary, treating with an alkalineagent such as sodium or ammonium hydroxide in sufiicient amount torender the resulting product substantially neutral.

The flame-resistant composition is prepared by incorporating the acidpetroleum sludge derivative in the bitumen. The bitumen may be heated toa temperature at which it becomes fluid and the acid sludge derivativemay then be added and the mixture stirred to produce the composition.The bituminous composition so produced may be used directly to coatarticles, or it may cut back with a suitable solvent or treated toproduce an emulsion in any of the ways known in the art to produce thinliquid bituminous coating compounds.

Qrdinarily the acid petroleum sludge derivative should be used in anamount equal to about 1% to 10% by weight of the composition, althoughlarger amounts up to about 20% may in some cases prove desirable.

If desired, various modifying agents may be added to the composition tosecure particular properties. For example, various oils, asphaltites,and mineral fillers may be added to the compositions. These aremodifying agents wellknown for imparting special properties to bitumens.

By way of example, a composition embodying the invention and comprisinga bituminous vehicle and a sulphated product of petroleum hydrocarbonsis described in detail below. It is understood, however, that thespecific composition described below is not considered to limit the scopof the invention.

Any bitumen having the desired physical properties may be employed asthe vehicle, but in order that the completed composition will form asufficiently hard, non-sticky, flame-resistant coating on such articlesas insulated wires and roofing elements, a bitumen having a softeningpoint upwards of F. should be employed. (The softening points referredto herein are determined by the A. S. T. M. standardized ring and ballmethod.) For most practical purposes a bitumen having a softening pointfrom 210 F. to 250 F. is especially satisfactory. Bitumens of suchrelatively high softening points are desirable not only because they aresufficiently hard for most practical purposes, but also because ingeneral such bitumens catch fire less readily than the softer bitumensof lower softening points. A bitumen which catches fire only with somediificulty is more suitable for use in making up the new flame-resistantcomposition than a bitumen which ignites readily.

Asphalts are particularly suitable bitumens for use in preparing the newcomposition. Any available asphalt may be employed, including naturalasphalts, steam reduced asphalts, blown asphalts, and asph'altic residua(flux oils) of petroleum distillation. Especially satisfactory resultshave been obtained using an air blown flux oil having a softening pointfrom 225 F. to 240 F. in preparing a flame-resistant composition forcoating insulated wires.

Satisfactory flame-resistant compositions may be prepared byincorporating the sulphated (or phosphated) product in the bituminoussubstance, without any modifying agents being added. In many instances,however, it is desirable to employ other substances in the compositionto modify its physical properties and to enhance its flame-resistance.Oily tempering agents which increase the weather-resistant qualities ofthe composition and make it less likely to crack in cold weather or toflow or run in hot weather are especially desirable. The oily temperingagent may be virtually any vegetable, animal or fish oil, or fatty acidderived therefrom. Drying oils are highly satisfactory for use as theoily tempering agent but semi-drying or non-drying oils have been usedwith success. Such oils in admixture with the bitumen, while loweringthe softening point of the mixture, increase its Weather-resistingproperties and make it rather rubbery in quality, thus reducing itstendency to become brittle when cold, or fluid or semi-fluid when warmedto a moderately high temperature substantially below its softeningpoint. Oils capable of thus modifying the properties of asphalticmaterials 066ml] mom and similar bitumens are well known, and it is suchoils that are embraced by the term oily tempering agent.

The use of an oily tempering agent is desirable for the further reasonthat it can be made to increase the difficulty with which the bituminousvehicle is set afire, and hence to enhance the flame-resistance of thefinished composition. Among the oily tempering agents which may be usedwith success may be mentioned fish oils, such as menhadin oil, pilchardoil, sardine oil, and herring oil; fish oil fatty acids; animal oils andfats, such as whale oil and beef tallow; and vegetable oils, such as soybean oil, linseed oil, cottonseed oil, tung oil, coconut oil, peanutoil, etc. The oily tempering agent is added in suitable amount to theasphalt and other bitumen preferably while the latter is heated to afluid condition. In general about 70% to 95% of the asphalt is employedin admixture with about 30% to 5 of the oily tempering agent. Highlysatisfactory results have been employed using mixtures composed of about90% by weight of asphalt and about weight of the oily tempering agent.

The oil serves as a flux for the asphalt, materially reducing itssoftening point. For many purposes this is undesirable, and accordinglyit is generally best to blow the mixture of oil and asphalt with air ata sufliciently high temperature and for a suificient period of time toincrease the softening point to a satisfactorily high value, say from210 F. to 250 F. Such blowing treatment may be carried out inconventional asphalt blowing equipment and in the manner usuallyemployed for preparing blown asphalts. The temperature of the mixtureduring the blowing advantageously is about 450 F. to 600 F. It may insome cases be necessary to increase the temperature of the mixture whilethe blowin proceeds and as the softening point of the mixture increases.For example, blowing may be begun at about 450 F. and the temperature ofthe mixture may be increased as blowing proceeds to an ultimate value ofabout 600 F. In general, the softening point of the blown asphaltoilmixture should be above 175 F., and preferably from about 210 F. toabout 250 F., for use in preparing flame-resistant compositions suitablefor coating wires, roofing elements and the like.

The blown mixture of asphalt or other bitumen and oil or other oilytempering. agent is easier to handle in commercial operations than theasphalt alone, is more rubbery than the asphalt alone, and is lesslikely to crack in cold weather and less likely to run or flow at highoutdoor temperatures. In addition it is less likely to bleed throughpaints applied over it on a wire or on a roofing element. It is,moreover, more difficult to ignite than the asphalt alone and so is abetter vehicle for the flame-resistant composition.

It may be mentioned at this point that mixtures of an asphaltic bitumenand an oily tempering agent can, by blowing for a sufficient period oftime, be made sufficiently flame-resistant so that when the blownmixture is applied to an insulated wire, the wire will pass-theUnderwriters flame test. however, the mixture must be blown at a hightemperature to an ultimate softening point of 300 F. or over. Blowingtosuch a high softening point is extremely hazardous, and the productobtained is markedly less flame-resistant than To accomplish thisresult,

properly prepared compositions according to the invention made withblown oil-asphalt mixtures of lower softening point.

Various other modifying agents, in addition to or in place of thegenerally preferred oily tempering agent, may be employed. For example,mineral fillers, hardening agents such as gilsonite or other asphaltite,and other modifying agents may be mixed with the bituminous base.

The composition is completed by incorporating in the bituminous vehiclea sulphated (or phosphated) product of a petroleum hydrocarbon, whichproduct is characterized by puffing and becoming highly intumescent whenexposed to flame. Not all hydrocarbon sulphates or phosphates puff andbecome intumescent when exposed to flame, and compounds not possessingthis property are not efiective in the new composition. For example,tricresyl phosphate does not possess this property a o-is not-satisfactory for use in the composition. However, the necessaryproperty of puffing and becoming intumescent when exposed to flame ischaracteristic of a great many sulphated and phosphated products ofpetroleum hydrocarbons, and all such compounds so characterized may beused with success. The suitability of any particular compound is readilyascertained by the simple test of exposing a small sample of thecompound on a spatula to a flame, and observing whether or not it puffsand becomes intumescent.

sulphated and phosphated derivatives of petroleum hydrocarbons suitablefor use in the new composition commonly are prepared by treating apetroleum hydrocarbon with concentrated sulphuric or phosphoric acid.Substantially pure sulphated or phosphated derivatives may be employed,but it is generally more economical to employ commercially availablereaction mixtures resulting from the treatment of petroleum productswith sulphuric acid. Particularly economical sulphated petroleumderivatives suitable for use in the new composition are the acidpetroleum sludge resulting from the treatment of petroleum products withsulphuric acid for refining purposes, and the acid oil resulting uponextraction of tar from such acid sludge. These materials are of complexcomposition but usually contain monoand di-alkyl sulphuric esters, somealcohols, sulphonated aromatic compounds, oxidation and condensationproducts, and polymerization products.

Acid sludge and acid oil, and other sulphated and phosphated productsresulting directly from treatment of petroleum products with sulphuricor phosphoric acid, are acidic. Although such compounds are effectivefor producing flameresistant compositions, the presence of acidconstitutents in compositions for coating such articles as wire androofing elements is generally undesirable. Accordingly, it is preferredto employ neutralized sulphated or phosphated products in making up theflame-resistant composition.

Methods are known for neutralizing acid sludge and similar acidicmaterials by treating with water or steam to dissolve the acid and causeit to separate from the oily constituent. After separation of the water,which contains the bulk of the acid dissolved therein, the residual oilymaterial may be treated with an alkaline material, such as sodium orammonium hydroxide, to neutralize such acid as remains. Neutralizedproducts of other acidic sulphated or phosphated petroleum compounds maybe prepared similarly.

Many neutralized sulphated (and phosphated) petroleum hydrocarbons arewater-soluble. Water-soluble compounds generally are undesirable for usein the new composition, because many of the articles coated therewithmust be exposed to the weather. Water-soluble constituents in acomposition so exposed will eventually be washed away. Moreover,water-soluble sulphated or phosphated derivatives of the characterherein described are in some cases capable of functioning as soaps, andare likely to cause the bitumen (or other vehicle of the composition) toemulsify and wash away. It is therefore preferred to employwater-insoluble neutralized sulphated or phosphated compounds in thecomposition.

Such water-insoluble compounds may be prepared by treating thewater-soluble neutralized sulphated or phosphated derivative with thesalt of a metal capable of precipitating an insoluble product. Salts ofmetals known to form substantially water-insoluble soaps, such, forexample, as salts of calcium, copper, aluminum, lead, barium, etc., maybe employed to precipitate such insoluble sulphated or phosphatedproducts from neutralized acid sludge or the like. The water-insolubleproduct advantageously is precipitated by adding a water-soluble salt ofthe precipitating metal, as, for example, calcium chloride or coppersulphate, to the water-soluble material. The insoluble compound isprecipitated and separates as a water-insoluble solid or viscous oilylayer.

Water-insoluble neutralized sulphated or phosphated petroleumhydrocarbons also may be prepared by treating the slightly acidic sludgeresidue remaining after extraction of most of the acid from acid sludgewith the hydroxide of the metal selected to form the insoluble compound.For example, this slightly acidic residue may be treated directly withcalcium hydroxide to form a substantially neutralized water-insolublesulphated petroleum hydrocarbon mixture which is well suited for use inthe new composition.

The particular metal compound chosen to produce the insolubleneutralized sulphated or phosphated petroleum product is not critical.Calcium salts (or calcium hydroxide, depending upon the manner offorming the insoluble compound) are inexpensive and the calciumprecipitated product is generally highly eifective. In some cases it maybe desirable to employ a compound of some other metal so as to impartparticular properties to the insoluble product. The copper-precipitatedproduct, for example, is somewhat toxic to fungus growths, andcompositions prepared from such products are therefore especiallysuitable for use where resistance to deterioration from attack by fungiis important.

The sulphated (or phosphated) acid petroleum sludge derivative,preferably neutralized and water-insoluble, is readily incorporated inthe bituminous vehicle while the latter is heated to a fluid condition.The sulphated derivative may be added to the fluid vehicle, and themixture may be stirred or otherwise agitated to effect thoroughadmixture of the two components. The water-insoluble neutralizedsulphated derivative of acid sludge is soluble in bituminous vehiclesand is compatible therewith, so that no particular difliculty isexperienced in mixing the two together. An amount of the sulphated (orphosphated) product from 1% to 10% (or more if desired) by weight of thecomposition is generally effective for producing a highly flameresistantcomposition. A small amount within this range is effective if thebituminous base itself possesses moderate flame-resistance, whereas arelatively large amount within the stated range is desirable if the baseitself is fairly readily ignited. For most purposes, using anasphalt-oil base blown to a softening point of 210 F. to 250 F., about3% to 5% by weight of the sulphated product results in a compositionhaving excellent flame-resistance.

The new composition may be applied to articles in much the same mannerin which stearin pitch has heretofore been applied. For example, thecomposition may be applied to an insulated wire by drawing the wirethrough a molten bath of the composition, and thence through a wipingdie to remove excess composition. It may be applied to roofing sheets orother roofing elements by brushing the molten composition on to thesurface of the sheet, or by other methods commonly emplyed for coatingroofing elements with bituminous materials or with stearin pitch.

The new composition may readily be made sufiiciently flame-resistant sothat a rubberinsulated, fabriccovered wire coated therewith easilypasses the Underwriters flame test. In this connection it may be notedthat neither the vehicle of the new composition nor the sulphated orphosphated compound are by themselves particularly flame-resistant, andneither, when coated on a rubber-insulated wire, will by itself enablethe wire to pass the flame test. Bituminous vehicles of the characterherein specifically described burn quite readily, and the same isgenerally true of the sulphated or phosphated products of petroleumhydrocarbons. The latter, however, pufi" and become highly intumescentin the flame, and in consequence of this property the vehicle in whichit is incorporated is caused to puff and form an intumescent, difficultycombustible coky mass which is spaced from underlying inflammablematerial and so protects it from ignition by a flame.

The new flame-resistant composition can be made so as to be much lesssticky than stearin pitch b employing a non-sticky bituminous (or other)vehicle. A bituminous vehicle prepared from asphalt and an animal, fishor vegetable oil is, generally speaking, much less sticky than stearinpitch, and the composition prepared from such a base is correspondinglymuch less sticky. An advantage of the use of asphaltic residum (fluxoil) as the asphaltic component of the vehicle is that, when blown witha suitable oil to a high enough softening point, it yields a base havingno appreciable stickiness or tackiness at ordinary temperatures.

The new composition can be made considerably more flame-resistant thaneven the best grades of stearin pitch, and successive batches of the newcomposition can be prepared with uniformly high flame-resistantproperties. Because of the excellent flame-resistant qualities ofcompositions prepared according to the invention, it is possible toapply such compositions to insulated wire beneath relatively inflammablecoatings of asphalt or wax without destroying the flameresistanceimparted to the wire by the new composition. For example, stearin pitchhas heretofore been applied to wires to render them flameresistant byfirst saturating the fibrous jacket on the wire with an asphalticcompound, and applying the stearin pitch over the asphalt impregnatedjacket. Frequently a thin wax coating is applied over the stearin pitch,but where flame-resistance is desired the asphaltic constituents arealways applied under the stearin pitch. The new composition may beemployed to saturate the fibrous jacket, and asphaltic or wax (or both)finishing coats may b applied thereover.

The new composition can be made highly resistant to moisture penetrationby the selection of an appropriate vehicle. For example, compositionsmade with a bituminous base are substantially as moisture-resistant asthe straight bituminous vehicle. Hence such compositions may be employedto replace the asphaltic moisture-resistant saturate commonly applied towires and roofing compounds, without thereby sacrificing protection ofthe wire or roofing from moisture penetration, but with the attainmentof a considerable increase in protection against fire hazard.

The new composition is prepared from relatively inexpensive materials,and in its preferred form may be made more inexpensively than it ispossible to procure stearin pitch.

We claim:

1. A bituminous flame-resistant composition capable of being applied tothe surface of an article and of forming thereon a hard permanentcoating which is stable at temperatures incident to its normal use andis further characterized by pufing and coking with the formation of anintumesced diflicultly combustible coky mass when exposed to flame, saidcomposition being in the form of an intimate mixture consistingessentially of a bitumen having a softening point upwards of 175 F., towhich has been added a substantially neutral, water-insoluble sulphatedacid petroleum sludge derivative characterized by pufling and becominghighly intumescent when exposed to flame.

2. A bituminous flame-resistant composition capable of being applied tothe surface of an article and of forming thereon a hard permanentcoating which is stable at temperatures incident to its normal use andis further characterized by pufling and coking with the formation of anintumesced diflicultly combustible coky mass when exposed to flame, saidcomposition being in the form of an intimate mixture consistingessentially of a bitumen having a softening point upwards of 175 F., towhich has been added a substantially neutral water-insoluble acidpetroleum sludge derivative selected from the group consisting ofsulphated and phosphated sludge derivatives characterized by putting andbecoming highly intumescent when exposed to flame.

3. A bituminous flame-resistant composition capable of being applied tothe surface of an article and of forming thereon a hard permanentcoating which is stable at temperatures incident to its normal use andis further characterized by puffing and coking with the formation of anintumesced diflicultly combustible coky mass when exposed to flame, saidcomposition being in the form of an intimate mixture consistingessentially of a bitumen having a softening point upwards of 175 F., anda substantially neutral, water-insoluble acid petroleum sludgederivative selected from the group consisting of sulphated andphosphated sludge derivatives characterized by pufiing and becominghighly intumescent when exposed to flame, said composition having asoftening point upwards of 175 F.

4. A bituminous flame-resistant composition capable of being applied tothe surface of an article and of forming thereon a hard permanentcoating which is stable at temperatures incident to its normal use andis further characterized by puffing and, coking with the formation of anintumesced difficultly combustible coky mass when exposed to flame, saidcomposition being in the form of an intimate mixture consistingessentially of a bitumen having a softening point upwards of F., towhich has been added a phosphated acid petroleum sludge derivativecharacterized by puffing and becoming highly intumescent when exposed toflame.

5. An article of manufacture comprising a base structure having thereona coating of a bituminous flame-resistant composition which is stable attemperatures to which the article is normally subjected and which ischaracterized by pufling and coking with the formation of an intumesceddiificultly combustible coky mass when exposed to flame, saidcomposition being in the form of an intimate mixture consistingessentially of a bitumen having a softening point upwards of 17 5 F., towhich has been added a substantially neutral water-insoluble acidpetroleum sludge deriv ative selected from the group consisting ofsulphated and phosphated sludge derivatives characterized by puffing andbecoming highly intumescent when exposed to flame.

6. An article of manufacture comprising a base structure having thereona coatin of a bituminous flame-resistant composition which is stable attemperatures to which the article is normally subjected and which ischaracterized by pulling and coking with the formation of an intumesceddiflicultly combustible coky mass when exposed to flame, saidcomposition being in the form of an intimate mixture consistingessentially of a bitumen having a softening point upwards of 175 F., towhich has been added a substantially neutral water-insoluble sulphatedacid petroleum sludge derivative characterized by pufiing and becominghighly intumescent when exposed to flame.

7. An article'of manufacture comprising a base structure having thereona coating of a bituminous flame-resistant composition which is stable attemperatures to which the article is normally subjected and which ischaracterized by pulling and coking with the formation of an intumesceddiflicultly combustible coky mass when exposed to flame, saidcomposition being in the form of an intimate mixture consistingessentially of a bitumen having a softening point upwards of 175 F., towhich has been added a substantially neutral water-insoluble phosphated,

um s l udge derivative charac erized by becoming highly intumescent Whenexposed to flame.

JOHN W. OLSON. CHARLES W. BECHLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 2,339,853 Hemmer Jan. 25, 19442,305,324 Snyder Dec. 15, 1942 2,299,469 DAntal Oct. 20, 1942 2,071,354Morgan Feb. 23, 1937 1,888,295 Smith Nov. 22, 1932 (Other references onfollowing page) has..

Number Name Date 1,872,358 Styer Aug. 16, 1932 FOREIGN PATENTS 1,856,756Frigiola May 3, 1932 N mber n ry Date 1,842,857 Bolgar Jan, 26, 1932519,119 Great Britain d Mar. 18, 1940 1,834,552 Sadtler et a1. Dec. 1,1931 5 188,354 r at ta 1922 1,720,487 Lichtenstein July 9, 1929 01,663,577 Watson Mar, 27, 1923 THEE REFERENCES 1,444,051 Allison F b, 6,1923 ham, Asphalts and Allied Substances, 4th 1,231,935 Baskemue July 31917 ed. 1938, pages 45, 628, 720- 723. 1,167,195 Matter Jan. 4, 1916 10

